The addition of sterols and stanols to foods for their cholesterol-lowering properties and the resulting prevention of future diseases, such as atherosclerosis, heart disease and hypertension, has been known for years.
Since phytosterols and stanols are insoluble in water and only poorly soluble in fats and oils, the incorporation of these cholesterol-lowering agents in food preparations, cosmetic or pharmaceutical products poses considerable problems. The unfavorable solubility behavior of the substances results not only in poor dispersibility, but also in reduced bioavailability and in unsatisfactory stability of the food preparations. Accordingly, the prior art proposes numerous formulations for solving these problems.
Efforts to increase solubility included the formulation of esters of the sterols, as described, for example, in European patent application EP 1275309 A1, or esters of the stanols, as described in U.S. Pat. No. 5,502,045, which had slightly improved processability, but which also showed lower hypocholesterolaemic activity in relation to the free sterols. However, the esterified derivatives also show insufficient solubility to allow simple incorporation. Apart from the fact that the esterified sterols behave differently in their bioavailability, they also have other formulation properties through their different physicochemical character and necessitate the use of other auxiliaries.
Numerous patent applications describe how the availability of sterols can be improved by reducing their particle sizes, mainly by micronization. German Offenlegungsschrift DE 102 53 111 A1 describes powder-form phytosterol formulations with a mean particle size of 0.01 to 100 μm which can readily be redispersed in water. A process for the production of a sterol dispersion, in which the sterols have a particle size distribution of 0.1 to 30 μm, is disclosed in International patent application WO 03/105611 A2.
However, the micronization of the sterol particles is often not in itself sufficient to enable good incorporation to be achieved. Although the bioavailability of the finely dispersed particles can be improved by increasing the surface, the micronized particles show poor wetting behavior, readily aggregate and generally float on water-containing surfaces. In many cases, the ground sterol can only be dispersed in a beverage by special methods involving intensive mixing. However, intensive mixers are not normally available to the end user of the food manufacturers.
Accordingly, many manufacturers combine micronization of the sterols with the additional use of emulsifiers. One example of this are the preparations described in European patent EP 0897671 B1 which contain sterols and sterol esters with a particle size of at most 15 μm in a mixture with selected emulsifiers, the ratio by weight of emulsifier to sterol in the aqueous phase being less than 1:2. A particular disadvantage of these known preparations is that they tend to agglomerate.
Emulsifiers commonly used in foods are monoglycerides and polysorbates (U.S. Pat. No. 6,623,780 B1, U.S. Pat. No. 6,376,482 B2, WO 02/28204 A1). Powder-form sterol ester formulations having a low protein content and also containing mono- and diglycerides as emulsifiers are disclosed in International patent application WO 03/086468 A1. Even though these emulsifiers are distinguished by high compatibility and have been known for some time as food emulsifiers, efforts are being made to reduce the quantity in which such emulsifiers are used or even to avoid them altogether because emulsifiers also influence the bioavailability of other substances present in the foods or can adversely affect the stability of the formulations. Avoiding emulsifiers was also the goal of the sterol formulations disclosed in European patent EP 1059851 B1 which contain thickeners for better dispersibility. However, these preparations are not sufficiently stable.
Numerous other methods for improving solubility and dispersibility, such as formulation as emulsions, microemulsions, dispersions, suspensions or complexing with cyclodextrins or bile salts, are described in International patent application WO 99/63841 A1, which also mentions formulation in the form of preparations. PEG, PVP, copolymers, cellulose ethers and esters are proposed as carriers. The direct use of food bases as carriers for powdered sterols is also known, cf. EP 1 003 388 B1.
The choice of proteins as carriers for unesterified sterols and stanols is disclosed in WO 01/37681. Synergistic effects of sitosterol and soya proteins are described in EP 0669835 B1.
The problem addressed by the present invention was to provide compositions which would be free from the disadvantages described above and which would enable sterol and/or stanol esters to be simply and effectively dispersed in foods without any need for emulsifiers, more particularly such emulsifiers as lecithins, monoglycerides, diglycerides, polysorbates, sodium stearyl lactate, glycerol monostearate, lactic acid esters and polyglycerol esters. In addition, the sterol and/or sterol ester compositions would be simple to produce and would be distinguished over prior art compositions by good storage stability.